Magnetic behavior of bulk and fine particles of RCr 2 Si 2 C (R = La, Ce) compounds: possible magnetic ordering from Cr

Abstract

The magnetic behavior of the quaternary compounds, RCr 2 Si 2 C (R = La, Ce), has been investigated by magnetization ( M ) and heat-capacity ( C ) measurements (1.8–300 K) in the bulk polycrystals and nano forms (<1 µm) obtained by high-energy balling. Our finding is that Cr appears to exhibit magnetic ordering of an itinerant type at low temperatures (<20 K) in the bulk form, as inferred from a combined look at all the data. The magnetic ordering gets gradually suppressed with increasing milling time. Evidence for a mixed-valence state of Ce for the bulk form is obtained from the tendency of magnetic susceptibility to exhibit a maximum above 300 K. However, this feature vanishes in the nano form, which exhibits a Curie–Weiss behavior above 200 K as though Ce tends towards trivalency in these fine particles; in addition, there is a weak upturn in C / T below 10 K in the bulk, which becomes very prominent in the milled Ce-based specimens at lower temperatures, as though heavy-fermion behavior gets stronger in smaller particles.